modelLand_Fertility
Land fertility
Information
This model computes the land fertility as a function of its utilization. Land can be overused. If that happens, the fertility of the land shrinks. This is likely to happen as the overall world population continues to climb.
The land fertility is measured in kilograms of equivalent vegetable food per hectare and year. Arable land can be used to either grow vegetable food directly, or alternatively, to raise animals that then enter the human food chain. Yet it takes more land per human to raise animals than to grow vegetable food. For this reason, it is meaningful to convert proteines obtained from eating meat to equivalent units of vegetable food.
Notice that this model uses two different types of rate models. Whereas the yield technology rate is a so-called bi-flow, i.e., it can assume both positive and negative values leading to a change of flow direction, the land fertility integrator uses uni-flows, i.e., flows that are allowed to flow in the indicated direction only.
Parameters
| Type | Name | Default | Description |
|---|
| Real | des_food_ratio_dfr | 2 | Desired food ratio |
| Real | inherent_land_fert | 600 | Inherent land fertility |
| Real | land_fertility_init | 600 | Initial industrial investment |
| Real | t_policy_year | 4000 | Year of policy change |
| Real | yield_tech_init | 1 | Initial yield technology factor |
| Real[:] | p_yield_tech_chg_mlt | {0, 0, 0, 0} | Yield technology change multiplier |